How does Contention work

Hi,

I probably should know the answer to this question but am happy enough
to admit that I am confused.

Can someone answer the following questions about contention for me:

1. Is it ISP specific at my exchange? (i.e. I am having problem with
BTYahoo at the moment as presumably I am sharing my 50:1 connection
with lots of BT heavy users. If I move to another provider will these
BT heavy users still affect my service or will I inherit the new ISP's
heavy users impact?)

2. Can contention explain why my transfer rate graph, although
connected at 2Mbps, looks like this
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/. I am used to
starting a d/l and seeing it level out at whatever speed it can manage,
but currently it jumps up and down between 10 K\s and 200 K\s for the
length of the download

3. If I am gettting a different speed test result every time I run them
throughout the course of the day, ranging from 56 Kbps to 1.6 Kbps
whenevr I try, could this be a contention issue?

Basically, I am just trying to figure out if contention is the cause of
my problem or if I should be looking further into it?

BT have already done a line test and say there is nothing wrong. they
are putting it down to contention.

Any other BTYahoo customers having the same issue?

Cheers for any advice,

Gary

(E-Mail Removed) wrote in
news:(E-Mail Removed) oups.com:

> Can someone answer the following questions about contention for me:
>
> 1. Is it ISP specific at my exchange? (i.e. I am having problem with
> BTYahoo at the moment as presumably I am sharing my 50:1 connection
> with lots of BT heavy users. If I move to another provider will these
> BT heavy users still affect my service or will I inherit the new ISP's
> heavy users impact?)

I think it can occur both at the exchange (with other ADSL users on that
DSLAM regardless of ISP) and again in the connection pipe between BT and
your ISP, and finally also within your ISP's network! Each of these may
have different contention ratios. I understand that within exchanges things
are usually about 30:1 but the ISP may have only bought a 50:1 connection
to BT.

> 2. Can contention explain why my transfer rate graph, although
> connected at 2Mbps, looks like this
> /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/.

If you're using bittorrent that's not unusual, it depends on the torrent.

For speed tests, you really need to do them against a variety of targets,
e.g. your own ISP's speed test, plus I think there is a BT one you can
connect to directly, and comparing the two would help determine if the
contention is at the exchange or the ISP. I don't know the details of BT's
test pages though.

Thanks Horoyuki,

I am not using bit torrent though, or any for of P2P for that matter. I
never have.

I am talking about genuine downloads, and not from the same sites, from
anywhere on the web. I even notice when I RDP to my machine at work.

I have done the speedtest recommended to me by the BT helpdesk (on the
BT website) and I still see this happening there. Can never get the
maximum rate (ever) and always jumpy.

However the two BT guys I spoke to were adamant that because my 2Mbps
connection could download a 5.5 MB file in less than 3 minutes I had a
good connection. To such a degree in fact they have said they are
taking it no further as I do not have a problem.

My ISP is BT as well by the way.

Any thoughts?

On 24 Nov, in article
<(E-Mail Removed) .com>
(E-Mail Removed) wrote:

> Thanks Horoyuki,
>
> I am not using bit torrent though, or any for of P2P for that matter. I
> never have.
>
> I am talking about genuine downloads, and not from the same sites, from
> anywhere on the web. I even notice when I RDP to my machine at work.
>
> I have done the speedtest recommended to me by the BT helpdesk (on the
> BT website) and I still see this happening there. Can never get the
> maximum rate (ever) and always jumpy.
>
> However the two BT guys I spoke to were adamant that because my 2Mbps
> connection could download a 5.5 MB file in less than 3 minutes I had a
> good connection. To such a degree in fact they have said they are
> taking it no further as I do not have a problem.
>
> My ISP is BT as well by the way.
>
> Any thoughts?

The back of this 'ere envelope tells me that a time of 30 seconds is
possible, plus or minus, so either they've confused bits and bytes, or
they have some bad info in their helpdesk script. I'd be inclined to
play dumb/confused, and ask just how they worked it out.

Either way, I wonder if it is _slow_ enough to be a line fault. When I
had a bad-line problem, the connection had a bad habit of dropping
completely, but when it did work it wasn't slow. And my experience of
busy sites is that I could see bursty traffic, which might be averaged
out by speed-reporting software to turn spikes into a sawtooth pattern.

And don't neglect your ADSL filters and the cable between wallsocket and
modem. Again, not ADSL experience, but I have had problems which were
fixed by a new cable. Having a spare doesn't seem extravagant.







--
David G. Bell -- SF Fan, Filker, and Punslinger.

"I am Number Two," said Penfold. "You are Number Six."

Thanks David,

Probably should have mentioned this before but so far I have:

- Unplugged the router and taken it to the main socket
- Swapped out the filters
- tried on 3 different machines running different AV and Firewalls
- tried with different websites
- Had a line test performed by BT (in my home)
- Tried through the night to see if any difference.

Only things I can think of to try now are the MTU size set up on the
router and the actual router itself.

I will try and do these things this evening,

Its just very strange that BT are telling me that this is due to
contention yet for 4 months my line reported 2 Meg in every speed test
I performad and downloading from any website settled at between 220 and
240 K\s. Now it seems completely random at all times.

Also, I spoke to my upstairs neighbor who is on the same exchange and
they are hunky dory??

Im getting confused. :-)

Any suggestions greatly appreciated.

On 24 Nov 2005 09:14:20 -0800,it is alleged that (E-Mail Removed)
spake thusly in uk.telecom.broadband:

>Thanks David,
>
>Probably should have mentioned this before but so far I have:
>
> - Unplugged the router and taken it to the main socket
> - Swapped out the filters
> - tried on 3 different machines running different AV and Firewalls
> - tried with different websites
> - Had a line test performed by BT (in my home)
> - Tried through the night to see if any difference.
>
>Only things I can think of to try now are the MTU size set up on the
>router and the actual router itself.
>
>I will try and do these things this evening,
>
>Its just very strange that BT are telling me that this is due to
>contention yet for 4 months my line reported 2 Meg in every speed test
>I performad and downloading from any website settled at between 220 and
>240 K\s. Now it seems completely random at all times.
>
>Also, I spoke to my upstairs neighbor who is on the same exchange and
>they are hunky dory??
>
>Im getting confused. :-)
>
>Any suggestions greatly appreciated.

This is a long shot, but I have had the same thing with an elink
(probably badged no-name) router from Maplin, rebooting the router
solved the problem. Have you tried this?

--
"The perfect computer has been developed. You just feed in your problems
and they never come out again."
- Al Goodman.

Thanks Chip,

Have rebooted the router several times and last night I swapped it out
completely from a USB modem. Still the same problem.

I also changed my MTU size and swapped all the ADSL filters, as well as
disconnecting everything from the line except the brodband.

Still no joy.

Help!! :-)

<(E-Mail Removed)> wrote in message
news:(E-Mail Removed) ups.com...
> Thanks Chip,
>
> Have rebooted the router several times and last night I swapped it out
> completely from a USB modem. Still the same problem.
>
> I also changed my MTU size and swapped all the ADSL filters, as well as
> disconnecting everything from the line except the brodband.
>

What MTU figure's did you try?
Was this on the router within Windows or both?

Also, did you change your RWIN settings within Widows as you altered your
MTU?
If yes, what settings did you try with each MTU setting?
If no, it may be worth looking into as these settings have a direct
correlation with each other.

I ran a ping test to find my optimum MTU setting and got it at aroun
1450 so I set it to that.

Set it on teh router and on the PC.

And I dont know anything about the RWIN setting. Could this be causing
the problem I am experiencing?

Cheers,

Gary

<(E-Mail Removed)> wrote in message
news:(E-Mail Removed) ups.com...
>I ran a ping test to find my optimum MTU setting and got it at aroun
> 1450 so I set it to that.
>
> Set it on teh router and on the PC.
>
> And I dont know anything about the RWIN setting. Could this be causing
> the problem I am experiencing?
>

For info on both MTU and RWIN as well as tests and tweaks go here
http://www.dslreports.com/faq/6266
The site is not UK ADSL specific so the suggested values that they give have
to be taken with a pinch of salt.
The info though is fine

For a 2meg connection in the UK some figures that have been used by others
to good effect are:
MTU 1478 / RWIN 63272
MTU 1458 / RWIN 62392
MTU 1430 / RWIN 61160